Why does PHP 5.2+ disallow abstract static class methods?

user_47680 0
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After enabling strict warnings in PHP 5.2, I saw a load of strict standards warnings from a project that was originally written without strict warnings:

Strict Standards: Static function Program::getSelectSQL() should not be abstract in Program.class.inc

The function in question belongs to an abstract parent class Program and is declared abstract static because it should be implemented in its child classes, such as TVProgram.

I did find references to this change here:

Dropped abstract static class functions. Due to an oversight, PHP 5.0.x and 5.1.x allowed abstract static functions in classes. As of PHP 5.2.x, only interfaces can have them.

My question is: can someone explain in a clear way why there shouldn't be an abstract static function in PHP?

abstract static oop php
8 Answers

static methods belong to the class that declared them. When extending the class, you may create a static method of the same name, but you are not in fact implementing a static abstract method.

Same goes for extending any class with static methods. If you extend that class and create a static method of the same signature, you are not actually overriding the superclass's static method

EDIT (Sept. 16th, 2009)
Update on this. Running PHP 5.3, I see abstract static is back, for good or ill. (see http://php.net/lsb for more info)

CORRECTION (by philfreo)
abstract static is still not allowed in PHP 5.3, LSB is related but different.

user_671680

I would argue that an abstract class/interface could be seen as a contract between programmers. It deals more with how things should look/ behave like and not implement actual functionality. As seen in php5.0 and 5.1.x it's not a natural law that prevents the php developers from doing it, but the urge to go along with other OO design patterns in other languages. Basically these ideas try to prevent unexpected behavior, if one is already familiar with other languages.

user_1224890

I don't see any reason to forbid static abstract functions. The best argument that there is no reason to forbid them is, that they are allowed in Java. The questions are: - Are the technically feasable? - Yes, since the existed in PHP 5.2 and they exist in Java. So whe CAN do it. SHOULD we do it? - Do they make sense? Yes. It makes sense to implement an part of a class and leave another part of a class to the user. It makes sense in non-static functions, why shouldn't it make sense for static functions? One use of static functions are classes where there must not be more than one instance (singletons). For example an encryption engine. It does not need to exist in several instances and there are reasons to prevent this - for example, you have to protect only one part of the memory against intruders. So it makes perfect sense to implement one part of the engine and leave the encryption algorithm to the user. This is only one example. If you are accustomed to use static functions you'll find lots more.

user_29640210

Look into PHP's 'Late Static Binding' issues. If you're putting static methods on abstract classes, you're probably going to run into it sooner rather than later. It makes sense that the strict warnings are telling you to avoid using broken language features.

Sean_McSomething_394130
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